scholarly journals Synchrotron and Laboratory Studies Utilizing a New Powder Diffraction Technique

1992 ◽  
Vol 36 ◽  
pp. 653-661 ◽  
Author(s):  
G. S. Knapp ◽  
M. A. Beno ◽  
G. Jennings ◽  
M. Engbretson ◽  
M. Ramanathan
Keyword(s):  
Powder Diffraction ◽  
Sample Surface ◽  
X Rays ◽  
High Count ◽  
Synchrotron Source ◽  
Bent Crystal ◽  
Capillary Sample ◽  
Order Of Magnitude ◽  
New Type ◽  
Large Improvement

AbstractWe have developed a new type of powder diffractometer. The diffractometer has the potential of both high count rates and very high resolution when used at a synchrotron source. The laboratory based instrument can achieve an order of magnitude improvement in count rate over existing methods with proper optics. The method uses a focusing diffracted beam monochromator in combination with a multichannel detector. The incident x-rays fall on a flat plate or capillary sample and are intercepted by a bent focusing monochromator which has the focus of the bend at the sample surface. The powder diffraction lines emerging from the bent crystal monochromator are detected by a linear or 2-dimensional detector. This allows us to eliminate the background from fluorescence or other scattering and to take data over a range of 3° to 4° instead of one angle at a time thereby providing a large improvement over conventional diffractometers.

A new type of constraint in the maximum-entropy method using ambiguous phase information from anomalous-scattering powder data

1999 ◽  
Vol 55 (4) ◽  
pp. 719-728 ◽  
Author(s):  
K. Burger ◽  
W. Prandl
Keyword(s):  
Maximum Entropy ◽  
Powder Diffraction ◽  
Entropy Method ◽  
Anomalous Scattering ◽  
X Rays ◽  
Synchrotron Source ◽  
Structure Factors ◽  
New Type ◽  
Types Of Information

Anomalous scattering of X-rays at a synchrotron source can be used for the ab initio structure determination of unknown crystal structures using only powder diffraction data. For noncentrosymmetric crystals, the phases of structure factors can only be determined with a remaining ambiguity, when one chemical element is used as resonant scatterer. A corresponding additional constraint function has been built into an enhanced version of the program MEED, so that now all types of information gained from an anomalous-scattering powder diffraction experiment can be used in a maximum-entropy calculation of the electron-density distribution: phased reflections, unphased reflections, intensities of groups of overlapping reflections, and now also reflections with a remaining ambiguity in the phase. This is important for practical use, since a lot of information is already lost in the powder diagram compared with single-crystal datasets and it is essential to use all remaining information. The new constraint is demonstrated with the structure of Cu5Zn8.

POSITION-SENSITIVE X-RAY DETECTOR SYSTEM FOR HIGH RESOLUTION PIXE MEASUREMENTS

1992 ◽  
Vol 02 (03) ◽  
pp. 263-268 ◽  
Author(s):  
H. Hamanaka ◽  
K. Hasegawa ◽  
Y. Yamamoto
Keyword(s):  
High Resolution ◽  
Delay Line ◽  
Detection Efficiency ◽  
X Rays ◽  
Good Position ◽  
X Ray ◽  
Sensitivity Distribution ◽  
Order Of Magnitude ◽  
New Type ◽  
Position Sensitive

A position-sensitive proportional counter with a carbon fiber anode, a goniometer and its associated electronics have been constructed to measure particle induced X-rays. The counter is easy to construct and its volume is about one order of magnitude smaller than a commercially available delay-line PSPC. This counter has good position linearity and uniform sensitivity distribution. Comparison is made between the new type of PSPC and an older one previously reported. It is shown that an enlargement of the X-ray window of the PSPC is effective for improving the detection efficiency.

In Situ Gas Supply System on the Powder Diffraction Beamline I11 at Diamond Light Source

2012 ◽  
Vol 706-709 ◽  
pp. 1707-1712 ◽  
Author(s):  
J.E. Parker ◽  
J. Potter ◽  
S.P. Thompson ◽  
A.R. Lennie ◽  
C.C. Tang
Keyword(s):  
Powder Diffraction ◽  
High Pressures ◽  
High Angular Resolution ◽  
X Rays ◽  
Double Crystal ◽  
Time Resolved ◽  
Double Crystal Monochromator ◽  
Harmonic Rejection ◽  
Capillary Sample

Beamline I11 at Diamond began accepting users for high resolution powder diffraction experiments in Oct 2008. We present the design, key specifications, performance and the hardware of this new beamline which receives an intense and highly collimated x-ray beam generated by an in-vacuum undulator. With the simple optics (a double-crystal monochromator, harmonic rejection mirrors and slits), a high purity beam of low energy-bandpass X-rays optimised at 15 keV is delivered at the sample. The heavy duty diffraction instrument is designed to have the flexibility to house a variety of sample environments and holds two detection systems to collect high quality diffraction data, i.e. multi-analysing crystals (MAC) for high angular resolution experiments and a fast position sensitive detector (PSD) for time-resolved studies. A recent addition to the beamline capabilities is the installation of a specifically designed gas control system. This allows the in-situ dosing of a powder sample with gases such as hydrogen and carbon dioxide, at low (~10 mbar) and high pressures (<100 bar). In addition a low pressure capillary sample cell is described which is now available to users of the beamline.

X-ray diffraction properties of curved crystal diffractors

1992 ◽  
Vol 50 (2) ◽  
pp. 1734-1735
Author(s):  
W. Z. Chang ◽  
D. B. Wittry
Keyword(s):  
Diffraction Theory ◽  
X Rays ◽  
Diffraction Image ◽  
X Ray Diffraction ◽  
Rocking Curve ◽  
X Ray ◽  
Bent Crystal ◽  
Diffraction Geometry ◽  
Crystal Parameter ◽  
Quantitative Procedure

Since Du Mond and Kirkpatrick first discussed the principle of a bent crystal spectrograph in 1930, curved single crystals have been widely utilized as spectrometric monochromators as well as diffractors for focusing x rays diverging from a point. Curved crystal diffraction theory predicts that the diffraction parameters - the rocking curve width w, and the peak reflection coefficient r of curved crystals will certainly deviate from those of their flat form. Due to a lack of curved crystal parameter data in current literature and the need for optimizing the choice of diffraction geometry and crystal materials for various applications, we have continued the investigation of our technique presented at the last conference. In the present abstract, we describe a more rigorous and quantitative procedure for measuring the parameters of curved crystals.The diffraction image of a singly bent crystal under study can be obtained by using the Johann geometry with an x-ray point source.

The Basic Physical Principles of Ion, Electron, and X-Ray Detectors and Their Application to Microanalysis

1985 ◽  
Vol 43 ◽  
pp. 154-157
Author(s):  
A.J. Tousimis
Keyword(s):  
Ion Beam ◽  
Depth Resolution ◽  
Sample Surface ◽  
High Energy ◽  
X Rays ◽  
X Ray ◽  
Electrons And Ions ◽  
Spatial Depth ◽  
Minimum Surface Area ◽  
Physical Principles

An integral and of prime importance of any microtopography and microanalysis instrument system is its electron, x-ray and ion detector(s). The resolution and sensitivity of the electron microscope (TEM, SEM, STEM) and microanalyzers (SIMS and electron probe x-ray microanalyzers) are closely related to those of the sensing and recording devices incorporated with them.Table I lists characteristic sensitivities, minimum surface area and depth analyzed by various methods. Smaller ion, electron and x-ray beam diameters than those listed, are possible with currently available electromagnetic or electrostatic columns. Therefore, improvements in sensitivity and spatial/depth resolution of microanalysis will follow that of the detectors. In most of these methods, the sample surface is subjected to a stationary, line or raster scanning photon, electron or ion beam. The resultant radiation: photons (low energy) or high energy (x-rays), electrons and ions are detected and analyzed.

X-Ray absorption edge elemental imaging of B. thuringienis

1989 ◽  
Vol 47 ◽  
pp. 212-213
Author(s):  
R. L. Stears
Keyword(s):  
Absorption Edge ◽  
Elemental Distribution ◽  
X Rays ◽  
Differential Absorption ◽  
Synchrotron Source ◽  
High Brightness ◽  
X Ray ◽  
Elemental Imaging ◽  
Cellular Integrity ◽  
X Ray Absorption

Because of the nature of the bacterial endospore, little work has been done on analyzing their elemental distribution and composition in the intact, living, hydrated state. The majority of the qualitative analysis entailed intensive disruption and processing of the endospores, which effects their cellular integrity and composition.Absorption edge imaging permits elemental analysis of hydrated, unstained specimens at high resolution. By taking advantage of differential absorption of x-ray photons in regions of varying elemental composition, and using a high brightness, tuneable synchrotron source to obtain monochromatic x-rays, contact x-ray micrographs can be made of unfixed, intact endospores that reveal sites of elemental localization. This study presents new data demonstrating the application of x-ray absorption edge imaging to produce elemental information about nitrogen (N) and calcium (Ca) localization using Bacillus thuringiensis as the test specimen.

NEUTRON POWDER DIFFRACTION AND OXIDE SUPERCONDUCTORS

1993 ◽  
Vol 07 (16n17) ◽  
pp. 3077-3093 ◽  
Author(s):  
A.W. HEWAT
Keyword(s):  
Heavy Metals ◽  
High Temperature ◽  
Powder Diffraction ◽  
Neutron Powder Diffraction ◽  
Oxide Superconductors ◽  
X Rays ◽  
New Materials ◽  
Oxidation Reduction ◽  
High Temperature Oxide ◽  
Temperature Oxide

Neutron powder diffraction has been essential for understanding the structures of the new high temperature oxide superconductors because of the difficulty in locating oxygen with X-rays in the presence of heavy metals, especially when single crystals are usually not available. This understanding lead to the discovery of new materials. In this paper we will show how it also sheds light on the crystal chemistry of oxide superconductors—the effects of oxidation/reduction, phase separation, pressure etc.

Applications of High-Resolution Powder X-Ray Diffraction

2007 ◽  
Vol 130 ◽  
pp. 7-14 ◽  
Author(s):  
Andrew N. Fitch
Keyword(s):  
High Resolution ◽  
Synchrotron Radiation ◽  
Powder Diffraction ◽  
X Rays ◽  
X Ray Diffraction ◽  
Crystalline Materials ◽  
X Ray ◽  
Structural Characterisation ◽  
Pdf Analysis

The highly-collimated, intense X-rays produced by a synchrotron radiation source can be harnessed to build high-resolution powder diffraction instruments with a wide variety of applications. The general advantages of using synchrotron radiation for powder diffraction are discussed and illustrated with reference to the structural characterisation of crystalline materials, atomic PDF analysis, in-situ and high-throughput studies where the structure is evolving between successive scans, and the measurement of residual strain in engineering components.

Crystallization and preliminary structural studies of Scilla campanulata lectin complexed with α1–6 mannobiose

1998 ◽  
Vol 54 (1) ◽  
pp. 90-92 ◽  
Author(s):  
Lisa M Wright ◽  
Stephen D. Wood ◽  
Colin D. Reynolds ◽  
Pierre J. Rizkallah ◽  
Anthony K. Allen
Keyword(s):  
Molecular Replacement ◽  
X Rays ◽  
Synchrotron Source ◽  
Replacement Method ◽  
Cell Dimensions ◽  
Molecular Replacement Method ◽  
Hanging Drop Method ◽  
Unit Cell Dimensions ◽  
Antiretroviral Activity ◽  
Image Plate System

Recent work has shown that Scilla campanulata agglutinin from bluebell bulbs has a strong affinity for α(1,3)- and α(1,6)-linked mannosyl residues and possesses moderate antiretroviral activity. This lectin has been crystallized by the hanging-drop method of vapour diffusion complexed with the disaccharide mannose-α1,6-D-mannose. The crystals are in the space group P21212 with unit-cell dimensions a = 70.63, b = 92.79 and c = 47.25 Å, and with a dimer in the asymmetric unit. The crystals diffract X-rays to beyond 1.5 Å resolution at 277 K and are stable in an X-ray beam. Data to 1.6 Å resolution have been collected using a MAR image-plate system at a synchrotron source and the structure of the complex has been solved by the molecular replacement method.

Sign in / Sign up

Export Citation Format

Share Document